An acrylic rubber is used as functional parts, security parts, and the like centralized in the surrounding of the engine of automobiles and a gasket is one of major product forms among them.
However, the gasket is obtained by kneading compounding agents such as a filling agent and a vulcanizing agent with an unvulcanized rubber and then molding the mixture by vulcanization, but in case of the acrylic rubber, there are problems that since the rubber adheres on a roll on kneading, is hardly smoothed on sheeting, or is non flowable on molding, processability is poor and since vulcanization speed is slow or post-cure for a long time is required, curability is poor. Further, there are also problems such as the reliability of sealing and the necessity of high-precision processing of flange face.
Those in which processability and curability were improved are reported (Patent Document 1), but it does not enable the improvement of productivity by optical curing which enables rapid curing.
Further those in which a silicone material or an urethane (meth)acrylate resin is a main component are used as a gasket material, but when the silicone material is used, damage is serious when SJ grade engine oil being recent high performance engine oil, transmission oil for an automatic car and a portion of gear oil are used; therefore it has been in a situation that such damage cannot be solved by conventional technology such as a method of compounding basic zinc carbonate in which the contents of iminoxysilane and zinc hydroxide is 5 to 50% by weight (hereinafter, referred to as %) (Patent Document 2).
On the other hand, when those in which the urethane (meth)acrylate resin is a main component are used, there are those superior in oil resistance (Patent Document 3), but since it has ether bonds or ester bonds in main chain, there is a problem in heat resistance for a long time.
The present inventors have hitherto reported a polymer in which its main chain is an acrylic polymer obtained by living radical polymerization and which has a (meth)acryloyl group at its ends (Patent Documents 4 and 5), but compression set which is essential physical property as a gasket is not described.    Patent Document 1: JP-A-2000-154370    Patent Document 2: JP-A-3-203960    Patent Document 3: JP-A-64-112    Patent Document 4: JP-A-2000-72816    Patent Document 5: JP-A-2000-95826